# Tumor-infiltrating terminally exhausted CD8+ T cells augment the suppressive microenvironment within solid tumor

> **NIH NIH F30** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2021 · $51,036

## Abstract

PROJECT SUMMARY/ABSTRACT
Blockade of co-inhibitory ‘checkpoint’ molecules, PD-1 and CTLA-4, has induced impressive clinical responses
in advanced tumors; yet only in a subset of patients. Limited success with checkpoint blockade therapy suggests
other cell extrinsic or intrinsic mechanisms may be dampening an effective immune response. Cytotoxic CD8+
T cells (CTL) encountering chronic antigen and environmental stressors (e.g. hypoxia, nutrient deprivation) can
be driven to a terminally differentiated state marked by hyporesponsiveness and epigenetic, transcriptional, and
metabolic dysfunction; a cell fate known as ‘exhaustion’. However, it remains unclear whether terminally
exhausted CTL (Texh) are simply non-functional or instead possess tolerogenic or suppressive properties. Our
lab has conducted transcriptional profiling of tumor-infiltrating CD8+PD-1int (progenitor exhausted) CTL versus
CD8+PD-1hiTim-3+ Texh, revealing that exhausted cells express a pattern of genes associated with immune
regulation. Among these is the ectonucleosidase, CD39, responsible for hydrolyzation of extracellular ATP
(eATP) to AMP. eATP is released upon T cell activation or cell death and induces proinflammatory cascades in
numerous cell types. Because depletion of eATP can limit T cell activation, CD39 expression on Texh is likely to
directly influence effector functions and tolerance in the tumor microenvironment. Indeed, when sorted directly
from tumor, Texh, but not progenitor exhausted CTL, induce marked suppression of T cell effector responses.
Strong preliminary in vitro data has revealed a HIF1a-dependent mechanism for CD39 expression in CTL. In
cancer patients, disruption of tumor hypoxia through metformin treatment or VEGFR inhibition improves
response to immunotherapy. Thus, we hypothesize that tumor hypoxia-driven CD39 expression on Texh
represents a major barrier to the anti-tumor immune response. Our data support a model that as CTL
progress to terminal exhaustion, hypoxic exposure upregulates CD39, providing Texh a mechanism to suppress
proinflammatory processes. These findings suggest that Texh are deleterious to anti-tumor immunity and may
need to be drastically reprogrammed or deleted in order to alleviate the immunosuppressive tumor
microenvironment.

## Key facts

- **NIH application ID:** 10076548
- **Project number:** 5F30CA247034-02
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Paolo Dario Angelo Vignali
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $51,036
- **Award type:** 5
- **Project period:** 2019-12-06 → 2023-12-05

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10076548

## Citation

> US National Institutes of Health, RePORTER application 10076548, Tumor-infiltrating terminally exhausted CD8+ T cells augment the suppressive microenvironment within solid tumor (5F30CA247034-02). Retrieved via AI Analytics 2026-06-11 from https://api.ai-analytics.org/grant/nih/10076548. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*